The present invention relates to the production of an adaptive deformable mirror for compensation of defects of a wavefront.
Adaptively deformable mirrors are used in various fields of optics, thus e.g. in terrestrial or extraterrestrial applications but also in experiments with electromagnetic radiation with high power, as is emitted by high-power lasers and/or high-power laser processes or in experiments with low or extreme ultraviolet radiation.
In particular for use with low or extreme ultraviolet radiation, various embodiments of adaptive mirrors have been developed. The basic idea resides in a mirror surface being deformed by means of actuators such that defects in an incident wavefront can be compensated for. The actuators can act, on the one hand, perpendicular to the mirror layer and, on the other hand, can be applied in the form of layers. According to the field of application, the thickness of the mirror layer and/or of the actuators or of the active layer can be varied over the diameter of the adaptive mirror. By varying the thickness of the active layer, different forces can be adjusted for the deformation of the mirror substrate as a function of the radial position. The change in layer thickness is thereby effected continuously and constantly. Because of the high power of the incident radiation and the absorption thereof, the result can be deformations of the mirror layer. One possibility for avoiding such undesired deformations is offered by an adaptive mirror, the mirror frame of which, consisting of the same material as the layer on which the mirror surface is applied, acts as heat sink and hence cools the mirror membrane. Furthermore, adaptive mirrors have been proposed, the curvature of which is variable and which hence can be used in various fields of application.
The previous state of the art demands high manufacturing and mounting complexity in order to connect the actuators or the active layers correspondingly to the mirror surface and/or in order to produce permanently the desired curvature of the mirrored layer. Furthermore, because of the large layer thickness of the mirror surface, the result is thermal deformations which are caused by the high power of the incident radiation. These thermal deformations must then be compensated for in conventional adaptive mirrors with the help of the actuators, in addition to the defects in the wavefront, which makes the precise compensation of defects in the wavefront difficult.